1. Field of the Invention
This invention relates to optical disc drives and, more particularly, to control system and control method for moving an optical pickup unit to discriminate optical discs.
2. Description of Related Art
Nowadays, optical discs are widely used for storing information. There are various types of optical discs, such as CDs, DVDs, and Blu-ray Discs, with various specifications.
An optical disc drive is usually required to be capable of recording and/or reproducing data onto and/or from the different type optical discs. Generally, during recording/reproducing, the optical disc drive needs to move a pick-up unit to a predetermined position so as to make light beams emitted by the pick-up unit to be accurately focused at a predetermined track on the disc. In order to move the pick-up unit to the predetermined position, a moving direction and a moving distance should be accurately calculated. For example, when a disc is loaded into the optical disc drive, a first thing is to discriminate the type of the loaded disc. Therefore, the optical pickup unit is needed to be moved to a predetermined position for discrimination of the type of the loaded disc.
Referring to FIG. 6, a traditional optical disc drive 10 which is capable of discriminating types of optical discs is illustrated. The optical disc drive 10 includes a spindle motor 12, an optical pickup unit 14, and a driving apparatus 16 for moving the optical pickup unit 14. The driving apparatus 16 includes a sled motor 162, a sled shaft 164, and a sensor 166. An optical disc 20 is arranged on and rotated at a predetermined velocity by the spindle motor 12. The optical pickup unit 14 is disposed to face a read-out surface of the optical disc 20. The optical pickup unit 14 can be moved along a radial direction of the optical disc 20 by the sled motor 162 and the sled shaft 164.
The optical disc 20 includes a plurality of spiral recording tracks (not shown) extending from an inner side to an outer side thereof. Generally, data recorded on the optical disc 20 is read from the inner side to the outer side. Therefore, the optical pickup unit 14 is moved from the inner side to the outer side along the radial direction of the optical disc 20 during a reproducing process. Before the reproducing process, the optical disc 20 should be discriminated. A preferred predetermined point to discriminate the optical disc 20 is a start point of a data area 22. To discriminate the optical disc, the optical pickup unit 14 is first moved to an innermost position A of the optical disc 20 and then moved from the innermost position A to the predetermined point.
The optical disc drive 10 employs the sensor 166 to detect whether the optical pickup unit 14 has reached the innermost position A. The sensor 166 can be a switch. If the optical pickup unit 14 reaches the innermost position A, the sensor 166 is triggered and generates a detecting signal to indicate that the optical pickup unit 14 has reached the innermost position A. The detecting signal is used to prevent the optical pickup unit 14 from further moving. After reaching the innermost position A, the optical pickup unit 14 goes astern toward the predetermined position to discriminate the optical disc 20.
However, the structure of the traditional optical disc drive 10 is complex as the sensor 166 is critical and must be employed to detect whether the optical pickup unit 14 has reached the predetermined innermost position A.
Therefore, an optical disc drive with a simplified structure is desired.